What is the Difference Between XRF & ICP to Determine the Value of Your Converters?

When you ship your converters to a toll refiner, the assay analysis conducted determines the precise composition of platinum, palladium, and rhodium in your lot. During this analysis, toll refiners employ two predominant technologies: XRF and ICP.

But what sets these two analysis methods apart? Is one superior to the other? To answer these questions, let's examine how these technologies work.

What is XRF?

An X-Ray Fluorescence benchtop machine is a non-destructive method used to analyze elemental composition of your material.

How Does XRF Work?

In the machine, a source produces an X-ray and the beam enters your sample by a few micrometers. As a result, the atom in the sample is excited, causing an electron to be expelled from its inner shell.

This forces all the other electrons rearrange themselves, filling the void left by the ejected electron. By changing places and moving around, the electrons release energy as fluorescence. That creates a unique fingerprint or signal for each element, such as platinum, palladium, and rhodium.

The energy signal is measured to determine the concentration of each precious metal. Higher signals indicate higher concentrations, while lower signals indicate lower concentrations. A report is then generated, highlighting the detected elements within the sample.

What is ICP?

The Inductive Coupled Plasma machine, otherwise known as ICP, measures a sample by light intensity to determine the platinum, palladium, and rhodium concentration in your converters.

How does ICP Work?

The sample taken from your converter load is turned into a liquid form. Then, it’s aspirated by a pump until it reaches the nebulizer, where it mixes with Argon gasses to create small droplets that get into the spray chamber.

In the spray chamber, the finest droplets are separated from the biggest and are sent into the plasma, which burns at 10,000 degrees Celsius. At this incredibly hot temperature, all the atoms of the sample absorb huge amounts of energy. And when the energy is expulsed from the plasma, it releases light. Depending on the element we are measuring, the light emitted will be on different wavelengths.

To determine the concentration of each element, we measure the intensity of those wavelengths and voila, we got the concentration of PGMs in your load!

Now, the question arises: How do these methods differ in terms of determining value? And which instrument is better for achieving accurate material analysis?

The Differences Between XRF & ICP

XRF and ICP machines differ on three aspects: accuracy, time, and investment. Before we dive in, remember that the first step to achieve accurate results is preparing a proper sample.

What is a Proper Sample Preparation?

For accurate results, samples must be ground into fine particles with a consistent mesh rate to ensure appropriate particle size and homogeneity. Additionally, the measurement of humidity and carbon content is necessary as they can impact the material's weight and analysis results.

Time

XRF machines require significantly less time to analyze a sample compared to ICP, which requires a huge time investment. However, both methods require proper sample preparation and machine calibration beforehand, which takes a lot of time as well.

Accuracy

While XRF machines produce a relatively fast analysis, this method is not as accurate as ICP. It’s important to note here that accuracy depends heavily on proper sample preparation, so with a correct sample, XRF analysis can still be very precise.

On the other hand, ICP has excellent accuracy. There’s a reason why it’s considered the industry golden standard!

Capital Investment

In terms of financial investment, XRF machines require a lower capital investment compared to ICP machines. However, this does not imply that XRF machines are incapable of producing accurate and reliable results. With proper sample preparation, XRF machines can achieve a high level of accuracy. On the other hand, ICP machines require a significant capital investment, but they consistently deliver highly accurate results.

So, XRF or ICP?

In the processing industry, it’s always better to do too much rather than not enough. That means using both the XRF benchtop machine and the ICP machine to analyze your material. That’s because your bottom line relies on the accuracy of your results, so when both analysis methods are used, maximum accuracy is achieved.

But it’s not all processors who use both, so remember to stay informed and ask your processor what their analysis methods are.

Another critical factor to get accurate results is proper sample preparation. Without a correct and thorough sample preparation method, the analysis results will be inaccurate, and the determined value of your material will not reflect its true worth. So, make sure your toll refiner has the proper sample preparation method.

At PMR, we use both XRF and ICP methods, allowing us to provide you with the most accurate and reliable value for your material. If you would like to learn more about our processing methods, please visit our Toll-Refining page to stay in the loop.

For more evaluation and processing knowledge, visit PMR’s Resource Center.